1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Orbital Energy

  1. Jan 30, 2005 #1
    Just want to confirm. If an object is in orbit,, around earth, for example, the its total energy is equal to half of its Eg. But what is its kinetic energy equal to? Is there another expression rather than Ek = 1/2mv^2?
  2. jcsd
  3. Jan 30, 2005 #2
    For circular motion:

    [tex]E_k = \frac{1}{2}m\frac{(2 \pi r)^2}{T^2}[/tex]

    With T the period of the orbital motion. Now if you equate the gravitational force to the centripetal force [itex]mv^2/r[/itex] and use the same expression as above for the velocity you get:

    [tex]T^2=\frac{(2 \pi r)^2 r}{GM}[/tex]

    Wich is Keplers law for circular orbits. Filling this expression in the kinetic energy expression:

    [tex]E_k = \frac{GMm}{2r}=-\frac{E_g}{2}[/tex]

    This shouldn't be too surprising as total energy is kinetic + potential energy and you already noticed this equalled half the potential energy.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Orbital Energy
  1. Energy for orbits (Replies: 4)

  2. Orbital Energy (Replies: 5)

  3. Orbits and Energy (Replies: 7)

  4. Energy of orbits (Replies: 1)

  5. Orbit and Energy (Replies: 20)